Polymers containing recurring 1, 2, 4-oxadiazole rings



a ma No Drawing. Filed Mar. 19, 1959, Ser. No. 800,383 13 Claims. (Cl. 260-78) This invention relates to novel nitrogen-containing polymers obtained by the reaction of diamidoximes With a dicarboxylic acid or amide-forming derivatives thereof. This invention further relates to polymers containing recurring 1,2,4-oxadiazole rings.

Polymers resulting from the reaction of dicarboxylic acids with diamines have had considerable commercial success. In general, polyamides are strong and resist abrasion. They are relatively unaffected by water. However, conventional polyamides undergo some degradation when subjected to light, particularly in the ultraviolet, and loss of strength under hydrolytic conditions.

This invention has as an object the production of new and useful polymers by the reaction of diamidoximes with a dibasic acid or amide-forming derivative thereof. A further object is provision of polymers having recurring intralinear 1,2,4-oxadiazole units. A still further object is to provide polymers which are resistant to hydrolysis. Other objects will appear hereinafter.

These and other objects are accomplished by reacting diamidoximes with dibasic carboxylic acids, including polymer-forming derivatives as more fully described below. The polymeric products finally resulting from this reaction contain recurring 1,2,4-oxadiazole intralinear' rings.

The monomers employed in the polymer-forming reaction of this invention are (1) diamidoximes, i.e., compounds of the formula wherein R represents a bond joining the two functional groups or an inert divalent radical, particularly aliphatic F R and X represents a replaceable monoradical known to enter polyamide-forming reactions, including hydroxyl,

United States Patent alkoxyl, mercaptan, halogen, amide radicals, or salt 1 groups.

Reaction of the two monomers gives polymeric acyl derivative of the amidoxime which can be converted into polymer containing recurring 1,2,4-oxadiazole intralinear rings as illustrated by the equation:

3,044,994 Patented July 17, 1962 higher temperature with or without a catalyst or acid acceptor.

The following examples further illustrate the prepara tion and properties of the polymers of this invention.

EXAMPLE 1 Reaction of Adipam-ide Dioxime and Adipyl Chloride zN NHa O(CH2)4C 010(01194001 II N HON NOH o 0 H2N\ /NH: C (CH:)4C l ON NOC (CH2)C- A solution of 3 g. (0.0172 mole) of adiparnide dioxime and 2.75 g. (0.0348 mole) of pyridine in 35 ml. of dimethylformamide and a solution of 3.15 :g. (0.0172 mole) of .adipyl chloride in 35 ml. of dioxane were added simultaneously with stirring with a 30-minute period to 50 ml. of dimethylformamide. After the solution was stirred for 30 additional minutes, it was poured into water, and the polymer was isolated by filtration and washed with methanol. Yield was 3.2 g. (66%), M.P. l40-150 C.

Analysis.-Calcd. for C H N O C, 50.7; H, 7.05. Found: C, 51.8; H, 6.92. v

[o =0.18 (0.2% in dimethylformamide) EXAMPLE 2.

Fusion of Polymeric O-Adz'pyl Derivative of Adipamiae Dioxime to a Polymeric 1,2,4-0xadiaz0le formamide, and precipitated by pouring into methanol,

giving 064g. of buff solid, M.P. 99103 C., [1 =0.09 (0.2% in dimethylformamide). A sample of a polymer made in the same manner had elemental analyses and IR spectrum corresponding to the polyoxadiazole structure.

EXAMPLE 3 Solution Polymerization of Terephthalamide Dioxime and Isophthaloyl Chloride 0001 HzN NH:

C- -C HON Non EN NH 2 2 o o y x +2HC1 .ON Not") A solution of 0.970 g. (01-005 mole) of pure ter a ephthalamide dioxime in 15 ml. of dry dimethylacetamide in a small dry flask fitted with a mechanical stirrer and swept continuously with dry nitrogen was stirred and chilled in a Dry-Ice acetone bath until a solid mush 1.49 g. (0.037 mole) of sodium hydroxide in 50 m1. of water was added, and then a solution of 3.50 g. (0.0172 mole) of isophthaloyl chloride in 100 ml. of benzene was added all at once. After a few seconds, a white formed. Then 1.015 g (0.005 mole) of pure isophthal- 5 solid separated in a mass which slowed the stirrer. Stiroyl chloride was added. The Dry Ice bath was replaced ring was continued for 15 minutes, and the mixture was with ice and gentle stirring was resumed. After five filtered. The solid was stirred with methanol, removed minutes at C. the reaction was allowed to warm to by filtration, and dried. The yleld of polymer was 5.2 room temperature. Approximately five minutes after g., 180 C. (dec.), inherent viscosity=0.3l (0.2% the addition of the acid chloride, a dropwise addition of 10 in dzmethylformamide). 1.490 g. (0.010 mole) of diethylaniline was begun. This Using the above general procedure, terephthalanude addition required about 20 minutes. After two hours of dioXime and adipyl chloride were also used in this type stirring, the solution had become somewhat viscous. To of polymerization. Chloroform and carbon tetrachloride it there was added 2 ml. of acetic anhydride and the soluwere used in place of benzene, and sodium bicarbonate tion was heated at 50-60 C. for two hours. The soluand sodium carbonate were used as bases. tion was poured into water in a Waring blendor and the EX HIPLE 22 polymer was isolated by filtration. The flufiy white polymer melted with decomposition at a temperature above Polymers F F f Dlflmldgxlmes and 300 C. Its inherent viscosity was 1.13 (0.2% in di- Dwarbvxylw Aclds methylacetamide) H l l'\ /NH,

Analysis.Calcd. for C H N O c 59.28; H 3.71 G HO C CH CO H N, 17.29. Found: 0, 59.05; H, 4.15; N, 16.50. a s

The infrared spectrum was in good agreement with HON NOE H the proposed structure. Films cast from dimethylacetamide showed these physical properties: tensile strength, :0 9500 lb./sq. in.; elongation, 6.6%; modulus in tension, 379,000 lb./ sq. in. The films were unattected by organic L H ll solvents but were degraded by boiling water. T f h h l d (1 O d z 08 wo grams 0 terep t aaml e loxime an g. EXAMPLES 4-20 of sebacic acid were ground together, placed in a tube, Using the general procedure of Example 3 with variand immersed in a 150 C. oil bath. The solid melted ous combinations of stoichiometric amounts of di-amito a thick, foaming mass. A slow stream of dry nitrogen doximes and dibasic acid chlorides with solvents and acid was passed through the melt. Heating was continued for acceptors, other polymeric O-acyl diamidoximes were five hours. The cooled brown solid was washed from similarly obtained. The following table summarizes the 5 the tube with dimethylformamide. The insoluble polyvariables in the examples. In the table, inherent viscosmer weighed 1.40 g. (38% yield). Its inherent visities were measured in (a) dimethylacetamide (0.2%), cosity was 0.16 (0.2% in trifluoroacetic acid). The in- (b) trifluoroacetic acid (0.2%), (c) cone. sulfuric acid frared spectrum of the polymer showed it to be mainly (0.5%), and (d) dimethylformamide (0.2%). a poly O-acyl amidoxime structure with some 1,2,4-oxa- TABLE I Ex- Diamidoxime Diacid Solvent Acid Viscosample Chloride Acceptor lty 4 terephthalscbacyl dimethylacetdiethylani- 0.43.

amide. amide. line. 5 sebacamide isopllithaldo do 0.30

O e --domun Na HPO 0.64 7 Hul ""J Li CO 0.21". R dimethyltetra' Na1HPO4. 0.17

methylene sultonc. 9 ..do do hcxamethyl none 009.

phosphoramide. 10 do scbaeyl dimethylacet- Na HPO 0.04.

amide. 11 .d0 do do triethyl- 0.19

amine 12 terephthalisophthaldo diethylam- 0.59.

amide: sebacoyl. line. amide (76: 24 molar ratio) 13 nmmidp rln dn N8nHPO4 insoli 14 adipamide -do do triethyl- 0. 1 1

amine 15 sebac mi n rlr pyridine 0.11. 16 diethylcyanamid none 0.08". 17- oxamide adipyl dioxane triethyl- 0.31%

amine 1R do NaOFf 0.22 19 adipamide do dimethyl sulfoxide triethyl- 0.06

acetone. mine. 20 ace n NaHCO 0.07

EXAMPLE 21 diazole units present. Fusion of sebacic acid mono- Interfacial Polymerization of Adipamide Dfoxime and amldoxlme Isophthaloyl Chloride H: HO own) (2 A solution of 3.00 g. (0.0172 mole) of adipamide 2 2 8 dioxime in 100 ml. water and 50 ml. of benzene was NOE stirred vigorously in a Waring Blendor.

A solution of gave a similar result.

EXAMPLE 23 Polymers From Fusion of Diamidoximes and Dicarboxylic Esters C(C'HmC CHaOi CQCOnCHs e N NOH I H2N NH? EXAMPLE 24' Polymers Front Fusion of Diamidoximes and N,N-Adipyl Imidazole ll tin A mixture of 1.022 g. (0.0042 mole) of N,N-adipyl imidazole and 0.955 g. (0.0042 mole) of sebacamide dioxime was heated in a small dry flask at 120 C. in an oil bath. The mixture melted to a yellow viscous liquid. The temperature was held at 120 C. :for two hours and then was raised to 160C. over a two-hour period. The

HON

liquid became reddish amber, and on cooling it dried to a dark 'brown cake. The inherent viscosity of the polymer was 0.18 (0.2% in trifluoroacetic acid).

iii.

A suspension of 0.5 g. (0.0026 mole) of terephthalamide dioxime and 1.00 g. (0.0026 mole) of diphenyl dithiolsebacate in 5 ml. of dimethylacetamide was heated in an oil bath at 70 C. A clear solution resulted and after, a few minutes a white solid appeared. Heating at 70-75 C. was continued for two hours, and-then the suspension of white solid was poured into methanol, filtered, and washed well with methanol. The solid weighed 0.67 g. (72% yield). Its inherent viscosity was 0.31 (0.2% in trifluoroacetic acid). Heating terephthalamide. dioxime and diphenyl dithiolsebacate in an oil bath at 175200 C. for six hours at 1 mm. pressure resulted in a polymer with inherent viscosity of 0.16 (0.2% in trifluoroacetic acid).

EXAMPLE 25 Polymers by Reaction of Diamidoximes With Diphenyl Dithiolsebacate HgN NH:

o o 0 11 50 (0159 086 11 [1 ll HON NOE 0 0 H N\ NH2 O C c ZCoHsSH -'[()-N 5 EXAMPLE 2 Polymers by Reaction of Diamidoximes With the Pyridine Complex of Isophthaloyl Chloride NH -C W M Q NOH g N To a stirred solution of 0.88 g. of terephthalamide dioxime in dimethy-lacetamide there was added a suspension of 1.63 g. of pyridine-isophthaloyl chloride complex in dimethylacetamide. After two hours the solution was poured into aqueous methanol, and the precipitate was filtered. The polymer weighed 0.64 g.; inherent viscosity=0.06 (0.2% in dimethylformamide).

EXAMPLE 27 Polymeric 1,2,4-Oxadiazoles by the Action of Chemical Agents on Polymeric O-Acyl Diamidoximes O H2N NH? ll tr e tQ I. O n

A solution of 0.35 g. of high molecular weight polymer from terephthalamide dioxime and isophthaloyl chloride, 2 ml. of acetic anhydride, and 0.2 g. of trisodium phosphate in 25 ml. of dimethylacetamide was heated at C. for three hours. The solution was poured into methanol, washed with water, and dried. The infrared spectrum of the polymer indicates that most, but not all,

of the O-acylamidoxime oxadiazole rings.

Similar products were obtained when sodium acetate, arsenious oxide, or zinc oxide was substituted for t-ri sodiumphosphate as the basic catalyst.

EXAMPLE 28 groups were cyclized to 1,2,4-

Polymeric 1,2,4-0xadinzoles by Heating Polymeric O- Acyl Diamidoximes in Dimethyl Sulfoxide Solution 7 that the O-acyl dia-midoxime groups were substantially cyclized to 1,2,4-0Xadiazole rings.

EXAMPLE 29 Polymeric 1,2,4-0xadiazoles by Dry Heating of Polymeric O-Acyl Diamidoximes I A sample of polymer from 'terephthalamide dioxime and isophthaloyl chloride inthe form of a thin film was heated in an evacuated tube in a metal bath at 275" C.

for 10 minutes. Dehydration occurredeven"thoughthe J film did not melt. The infrared spectnum of the brittle amber film thus formed showed it to be largely polymeric 1,2,4-oxadiazole. 1

Temperatures from -300" C. canlbe used by vary-' ing the heating time as was determined by further experiments.

EXAMPLE 30 Polymeric 1,2,4-Oxadiazoles by Fusion of Polymeric -Acyl Diamidoximes A powdered sample of polymer from sebacamide dioxime and isophthaloyl chloride was heated in an evacuated fiask at ISO-180 C. for four hours. The solid melted and bubbles of water vapor were evolved. After cooling, the dark-brown solid was dissolved in dimethylacetamide and precipitated with ethyl acetate. Its infrared spectrum showed it to be a polyoxadiazole. The inherent viscosity was 0.54 compared to 0.29 for the starting material.

As shown by the preceding examples, the polymers of this invention have a plurality of either or both of the linear unit or the cyclic dehydration product N\ .C/ \C The polymers preferably have a relatively high molecular weight, the more useful ones having an inherent viscosity of 0.1 or higher, and in general a molecular weight of at least 2000.

In general the first polymeric product of the polymerforming reaction of the present invention does not contain oxadiazole rings, i.e., a S-membered heterocyclic ring having one oxygen and two nitrogen atoms, of which one of the latter is directly bonded to two carbon atoms. The first condensation product involves reaction of the hydroxylamino group with the dicarboxylic acid or a derivative of the dicarboxylic acid. Since the product thus has the hydroxylamino oxygen attached to carboxy or acyl carbon, it has been called a polymeric O-acyl derivative. These new polymers have the repeating unit wherein R and R can be the same or different and represent the means of joining two similar carbons of the i C (NHZ)=NO C- recurring groups, and m and n represent the same or different cardinal numbers form 0-1, R and R can be an inert divalent radical including hydrocarbon, especially alkylene and arylene diradicals of up to and including carbons. R and R can represent simply a bond (in the case of reaction products from oxamide dioxime or oxalyl dichloride). The preferred values for R and R thus include --(CH wherein y is a number of 0-10 and C H In other words, R and R include alkylene and arylene.

The new polymers containing a plurality of the O-acyl units are useful for the preparation of films and fibers by the means conventional in the polyamide art. It is generally diflicult to obtain polymers having the recurring O- acyl units in extremely high molecular weight. These polymers are susceptible to reaction and modification by virtue of the presence of the O-acyl units. Heating or use of dehydration conditions converts the O-acyl units to the 1,2,4-oxadiazole ring structure. The latter are generally of higher viscosity and are highly resistant to hydrolysis. Films and fibers prepared from the latter are useful for products that are subjected to acid or alkaline conditions as well as to heat and ultraviolet light.

The polymers having recurring 1,2,4-oxadiazole units, that is, those having the general structure unit wherein R, R, m and n have the same significance as indicated above, are particularly important since they are relatively inert. They are stable to hydrolytic conditions that break the bonds of linear non-cyclic polyamides.

As already mentioned, polymers of this invention are prepared by starting with diamidoximes which can be represented by the formula HZN NH, ;G R.. 0; HON NOH wherein R and m have the same significance as above. These amidoximes are obtained by the general process described by Lamb and White, J. Chem. Soc. 1939, 1253. Amidoximes that are useful include those of the formula wherein R and n have the values previously assigned and where X is a replaceable radical known to form amides with amines or esters with alcohols. Preferably, X is a radical selected from the group consisting of hydroxyl, alkoxyl, amino, thio, and halogen. In place of hydroxyl, i.e. dibasic carboxylic acids, salts of the acids can be used, e.g., amine and amide salts as well as alkali metal salts. For ease of reaction with the diamidoximes, it is preferred that X have a molecular weight of less than about 150.

The above dibasic acids and derivatives are recognized in polymer literature as polyamide-forming dibasic carboxylic compounds.

The conditions whereby polymers are formed from the diamidoximes and the dibasic carboxylic acid (or equivalent polyamide-forming derivative thereof) are subject to wide variation. They depend primarily on the reactivity of the acid or derivative. Temperatures for the reaction vary from below room temperature to the decomposition temperature of the polymer containing a plurality of the 1,2,4-oxadiazole units. The temperature range thus can vary from to 300 C. Low temperatures, e.g., 0 to 50 C. or below, are employed when dibasic acid chlorides are used while higher temperatures, e.g., -200 or above, are useful when dibasic acid is fused with the diamidoximes.

The presence or absence of inert solvents or diluents in carrying out the process of this invention depends on the method of reaction. When a dibasic acid is fused with the diamidoximes, solvents are generally undesired. Inert solvents are useful for some of the polymer-forming reactions that can be employed. Such solvents should dissolve the polymer-forming reactants as Well as the poly-' ing, e.g., at ISO-300 C. of O-acyl containing polymer whereby the heterocycle units are formed through the removal of water. 7

Polymers which have all, or 'at least the major portion, of the O-acyl units converted to 1,2,4-Xadiazole ring structures have increased viscosity and high softening points, decreased solubility, and increased stability toward hydrolytic or attack by ultraviolet light. The polymers of this invention are useful for the preparation of films and fibers. Films are particularly useful for packaging foods, particularly vegetables. p

The foregoing detailed description has been given for clearness of. understanding only and, no unnecessary limitations are to be understood therefrom. The invention is not limited to the exact details shown and described for obvious modifications will occur to those skilled in the art.

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

I claim:

1. Polymers consisting essentially of recurring units of the formula wherein R and R represent inert divalent hydrocarbon radicals having up to and including 10 carbon atoms.

2. Polymers consisting essentially of recurring 1,2,4- oxadiazole units represented by the formula 8. A polymer consisting essentially of recurring units of the formula 1 0 9; Polymers consisting essentially of'recurring units of the formula o HsN\ /NH2 (Ii, oN NOfii 0 10. Process which comprises reacting a diamidoxime selected from the class consisting of compounds of the formulas wherein R represents an inert divalent hydrocarbon radiical having up to and including 10 carbon atoms, and a polyamide-forming dibasic carboxylic compound selected from the class consisting of compounds of the formulas V 7 H [I II I Li 7 XCOX and. XCR- X wherein R represents an inert divalent hydrocarbon radical having up to and including 10 carbon atoms and X is a member of the group consisting of hydroxyl, alkoxyl, mercaptan, halogen, amino radical and salt groups.

ll. Process which comprises reacting a diamidoxirne selected from the class consisting of compounds of the formulas- HzN NHz HZN NH:

o-o and C-R-O HON NOH HON NOH wherein R represents an inert divalent hydrocarbon radical having up, to and including 10 carbon atoms, and a mem ber of the group consisting of compounds of the formulas wherein R represents an inert divalent hydrocarbon radical having up to and including 10 carbon atoms, and X is a member of the group consisting of 'hydroxyl, alkoxyl, mercaptan, halogen, amino radical and salt groups, and eliminating water from the resulting polymeric O-acyl derivative having a repeating unit selected from the group consisting of those of the following formulas wherein R and R represent inert divalent hydrocarbon radicals having up to and including 10 carbon atoms, to yield a polymer containing recurring intralinear oxadiazole rings.

l 1 12. Polymers consisting essentially 0 at least one member of the group consisting o f, as recurring units,

and

i \lil \I. L

having up to and including 10 carbon atoms.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3,044,994 July 17, 1962 Dale Clifton Blomstrom It is hereby certified that error appears in the above numbered petent requiring correction and that the said Letters Patent should read as corrected below.

Column 11, lines 3 to 8, the first formula should appear as shown below instead of as in the patent:

Signed nd sealed this 15th day of January 1963.

H2N NH2 (SEAL) Attest:

ERNEST W. SWIDER DAVID L. LADD Attesting Officer Commissioner of Patents 

1. POLYMERS CONSISTING ESSENTIALLY OF RECURRING UNITS OF THE FORMULA 